Saturday, April 27, 2013

New paper finds IPCC models predicted decrease in Antarctic sea ice, which is currently near record highs

A paper published today in the Journal of Geophysical Research - Atmospheres finds "most climate models from the [IPCC] archive simulate a decrease in Antarctic sea ice area over the recent past," however, "average Antarctic sea ice area is not retreating but has slowly increased since satellite measurements began in 1979." Further, the authors find the latest generation of IPCC climate models "have not improved" over the prior generation, and "show an unrealistic spread in the mean state that may influence future sea ice behavior."

The paper, co-authored by Climategate co-conspirator Susan Soloman, attempts to save face for the models, claiming the increase in Antarctic sea ice is still within natural variability. With Antarctic sea ice currently near 'unprecedented' high levels, how long can this IPCC model flimflam persist?

In contrast to Arctic sea ice, average Antarctic sea ice area is not retreating but has slowly increased since satellite measurements began in 1979. While most climate models from the CMIP5 archive simulate a decrease in Antarctic sea ice area over the recent past, whether these models can be dismissed as being wrong depends on more than just the sign of change compared to observations. We show that internal sea ice variability is large in the Antarctic region, and both the observed and modeled trends may represent natural variations along with external forcing. While several models show a negative trend, only a few of them actually show a trend that is significant compared to their internal variability on the timescales of available observational data. Further, the ability of the models to simulate the mean state of sea ice is also important. There presentations of Antarctic sea ice in CMIP5 models have not improved compared to CMIP3, and show an unrealistic spread in the mean state that may influence future sea ice behavior. Finally, Antarctic climate and sea ice area will be affected not only by ocean and air temperature changes but also by changes in the winds. The majority of the CMIP5 models simulate a shift that is too weak compared to observations. Thus, this study identifies several foci for consideration in evaluating and improving the modeling of climate and climate change in the Antarctic region.